Concepts Of Physics MCQ Edition [Volume 2]
- Exam
- Concepts Of Physics MCQ Edition [Volume 2]
- Subject
- Physics
- Chapter
- Photoelectric Effect and Wave–Particle Duality
Concepts Of Physics MCQ Edition [Volume 2] · Physics · Photoelectric Effect and Wave–Particle Duality
During a photoelectric effect experiment, the collector plate is...
During a photoelectric effect experiment, the collector plate is maintained vertically above the emitter plate. A light source is turned on, and a saturation photocurrent is measured. Following this, a vertically downward electric field is switched on.
Options
- AThe photocurrent will increase.
- BThe kinetic energy of the electrons will increase.
- CThe stopping potential will decrease.
- DThe threshold wavelength will increase.
Correct answer
B. The kinetic energy of the electrons will increase.
Step-by-step solution
The collector plate is placed vertically above the emitter plate, so the emitted photoelectrons travel in the upward direction.
When a vertically downward electric field is switched on, the force experienced by an electron of charge is . Since the electric field is directed downwards, the force on the electrons will be directed upwards.
This upward force acts in the direction of motion of the electrons, causing them to accelerate. As a result, the kinetic energy of the electrons will increase as they move towards the collector plate.
The saturation photocurrent depends only on the intensity of the incident light and the number of photoelectrons emitted per second, so it remains unchanged.
The threshold wavelength is a characteristic property of the emitter material (its work function) and is unaffected by the external electric field.
Because the electrons acquire additional kinetic energy from the electric field, a greater retarding potential would be required to stop them, meaning the magnitude of the stopping potential will increase, not decrease.
When a vertically downward electric field is switched on, the force experienced by an electron of charge is . Since the electric field is directed downwards, the force on the electrons will be directed upwards.
This upward force acts in the direction of motion of the electrons, causing them to accelerate. As a result, the kinetic energy of the electrons will increase as they move towards the collector plate.
The saturation photocurrent depends only on the intensity of the incident light and the number of photoelectrons emitted per second, so it remains unchanged.
The threshold wavelength is a characteristic property of the emitter material (its work function) and is unaffected by the external electric field.
Because the electrons acquire additional kinetic energy from the electric field, a greater retarding potential would be required to stop them, meaning the magnitude of the stopping potential will increase, not decrease.